I think your G3 will be also be viewed as an expensive camera, so I'm not sure it makes significant difference that way. I'm thinking along similar lines myself and I reckon this is a good way to look at it...

Set a weight limit for you gear. I'm thinking around 1kg perhaps 1.2kg. That would give an option of either your full G3 kit (I think) or your 5D2 and a single light prime lens, perhaps a 35mm or 50mm.

Looking at it that way what would you go for?

p.s. to lighten the load around your neck, have a look at a black rapid strap (or similar).

That's a good idea, sets a discipline I can work with. I take your point on the G3 being viewed as an expensive camera, but the security thing is not really a big concern for me. It was more about blending in, weight, wasting time juggling lots of kit and making kit choices rather than just shoot. And yes the black rapid, I bought the sports version for this trip - very nice!